How blood-borne viruses are spread

It is very unlikely that you will become infected through everyday social contact with another worker who has a blood-borne virus (BBV). It is not thought that BBVs can be transmitted via the respiratory route, although this possibility cannot be dismissed entirely when, under laboratory conditions, (such as high titre in vitro cultures), BBVs are present in concentrations far exceeding that found in normal body fluids. BBVs are mainly transmitted sexually or by direct exposure to infected blood or other body fluids contaminated with infected blood. In the workplace, direct exposure can happen through accidental contamination by a sharp instrument, such as a needle or broken glass. Infected blood may also spread through contamination of open wounds, skin abrasions, skin damaged due to a condition such as eczema, or through splashes to the eyes, nose or mouth.

Routes of transmission

Blood-borne viruses (BBVs) are transmitted by blood, or other body fluids containing virus. This happens when the blood or fluids enter into the body of a susceptible person. The rate of viral transmission varies depending on how the person has been exposed to the virus (the route of transmission), the type of virus, how much of the virus the carrier has in their body and the immune status of the exposed person.

The more common routes of transmission include:

• sexual intercourse (common for HBV, HIV; inefficient for HCV);
  
• sharing injecting equipment;
• skin puncture by blood-contaminated sharp objects (eg needles, instruments or glass); and
• childbirth (ie the mother infects the child either before or during birth, or through breast-feeding).

Less common routes of transmission are:

• contamination of open wounds (eg blood injuries during sporting activities);
• contamination of skin lesions (eg eczema);
• splashing of the mucous membranes of the eye, nose or mouth; and
• human bites when blood is drawn (this may be more of a problem in certain occupations, eg prison and police service, where front line workers may be exposed to violent behaviour).

There is also a risk of acquiring a BBV infection via blood transfusion. However, in the UK, all blood donations are screened for HBV, HCV and HIV, meaning the risk is remote.